Problems printing PMMA - walls are terrible

[novilis]

Dear colleagues,
I have been printing PMMA for a while now and the printing quality was always more or less ok. Never perfect, but ok. I am printing transparent PMMA.
Suddenly, the printer is facing a strange problem and not me or my colleagues can explain what’s going on. On some outer walls the print quality is really poor. Attached a photo. Do you have any ideas how this could have happened?
If I am using the same gcode on another Pro2 it works fine without these issues. If I reprint the same model on the faulty Pro2, the same errors appear.

Any help is appreciated!
Thanks,
Christian